Keep your money if you are just looking for Fuel Economy. Other than the usual stuff like tune up, keeping tires properly inflated you wont get enough of a difference in the milage mabey and that is a BIG mabey .25mpg i saw no difference with the hard cover or the soft cover on my 2006 Silvy.

If your main reason is to get better fuel economy, I absolutely agree with Murdog. I read a number of articles and have never heard of a truck bed cover (or removing the tailgate) really increasing MPGs. Beyond looking good, covers are also functional, as I use mine to hide and protect (even from weather elements) whatever I am carrying in my bed....it is this functionality that was my main reason for purchasing...MPGs were never a consideration.